Glossary of Terms
__NOWYSIWYG__ This is Locomotive Wiki's Please refer to this page for definitions of technical terms that appear in articles. See the /Manual for information regarding the editing of this glossary, as well as production history. A AAR Classification An axle notation system used by the USA in particular, and works as follows: A powered axle is shown by a capital letter, e.g. A = 1, B = 2 and so on; non-powered axles are represented by a number; trucks are separated by a hyphen "-"; and articulated chassis are denoted by a plus sign "+". adhesion The amount of grip a locomotive has on the rails. In certain conditions, e.g. wet weather, this may be reduced. articulation Where the frame, or set(s) of driving wheels, pivot to help a large locomotive navigate sharp curves. axle A spindle that joins a pair of wheels. axlebox Allows an axle to rotate freely via bearings. B bearing A part, usually metal, made out of rolling or sliding pieces that is fitted between moving parts to reduce friction, thus slowing wear and tear. blast pipe A pipe through which exhaust steam travels from the cylinders of a steam locomotive to be exited through the chimney. Blast pipes are located inside the smokebox. bogie Chiefly British form of truck. boiler A large drum in a steam locomotive that is filled with water and boiled to create steam. The steam then propels the locomotive. brake lever A lever that a driver of a locomotive can use to slow and/or stop a train. These can be found in all popular types of locomotive or multiple unit. brake shoe Piece of material that is pressed against a rotating object to slow a train. brick arch An arch of firebricks inside the firebox that funnels the hot gases evenly into the flue tubes. bunker Place for storing coal. Usually used in relation to tank locomotives. C cab The place where the driver can sit and operate a locomotive. caliper Part of the braking system in certain diesel and electric locomotives or multiple units. Only used with disc type brakes, the caliper squeezes brake shoes onto a rotating disc to slow and/or stop the train. This type of braking system is being replaced by dynamic braking (where traction motors exist) to avoid running costs and brake fade/failure. catenary Strictly, this describes the overhead wire that carries electric current for electric locomotives and EMUs. In common use, this term refers to all the wires, span cables, gantries etc. that completes an overhead power system. chassis Strictly speaking, this term refers only to the metal girders that give strength to a diesel or electric locomotive, onto which other components like the engine or body are bolted. Is sometimes used, however, to also describe the plates that hold on the body panels on diesel and electric locomotives. See also, frame. chimney A vent to allow exhaust gases to escape a steam locomotive. compounding A specific two-stage design of steam locomotive, whereby the steam is first used in high pressure cylinders then in low-pressure cylinders. Therefore, the steam is used most efficiently. connecting-rod ;Steam locomotive :Length of metal that connects the piston to the driving wheels and or coupling rod. ;Diesel locomotive :Connects the piston head with the crank-shaft inside a diesel engine. coupling rod A metal bar usually used in pairs to link the driving wheels together on each side of a locomotive. Used solely for when only one axle is powered. cowcatcher A wooden or metal cage-like structure on the front of a locomotive to move animals of the tracks. cylinder ;Steam locomotive :Where the steam is injected to push a piston back and forth. ;Diesel locomotive :Where diesel fuel is mixed with hot, compressed air to create an explosion that forces a piston to move away. D disc brake disc rotor Braking system where friction is used to slow the vehicle. The rotor(s), connected to the axle of vehicle, are squeezed by a caliper to cause the friction which is actually the force of the vehicle's momentum converted into heat. double-header driver driving wheel Alt: drivers. (Not to be confused with driver.) One of at least two wheels powered by a locomotive to achieve motion. E engineer Person works on a locomotive to keep it running correctly; or person who builds locomotives; or person who builds railroads. In the USA, may refer to the person controlling the locomotive. exhaust Gases left over after combustion or burning. Or steam left over after being through the cylinders. F firebox Place in a steam locomotive where fuel is burned creating heat to boil water in the adjacent boiler. flue tube The escape route for exhaust gases from the firebox through the boiler. Multiple flue tubes are used to heat the boiler up evenly. footplate The place (floor) from where the driver and engineer operate a steam locomotive. Is sometimes used as a synonym for running-plate. frame The metal plates and girders that hold a locomotive together. Is still in use for steam locomotives, but has fallen out of use of late for other types in favor of chassis. Can also refer specifically to the supports for the body panels of a diesel or electric locomotive. G gauge The distance between the rails a locomotive runs on. H hydraulic Using fluid pressure to operate something. I injector ;Steam locomotive :Used to get new water from the tender into the boiler by fighting the pressure within. ;Diesel locomotive :Sprays fuel into a cylinder. J junction Where two, or more, tracks are linked so that vehicles can transfer from one to another. K L locomotive A rail vehicle that propels itself. M maglev Abbreviation of "magnetic levitation"; the process of supporting a locomotive on magnetic fields. multiple unit Alt: multiple-unit; MU. A train made up of units that each have motors, or diesel locomotives coupled together. Either way the entire train is controlled from one cab, and by one engineer. N nth-header A trainset pulled by multiple locomotives. A common form is the double-header where two locomotives haul the train. O outside-framed Type of steam locomotive that has the frame on the outside of the wheels and running-gear. P pantograph An arm that holds a wire against a live cable above the track. See also, catenary. piston A cylindrical plug that moves back and forth inside a cylinder. priming Process in a steam locomotive where water is carried into the cylinders, as a result of using low-acidic water. Q R rail Used in parallel pairs to form a section of track, which the locomotive rolls on. resistor Component that slows down an electric circuit. It so works by converting the current into heat. rheostat A rheostat is a resistor that is adjustable. Used in rheostatic, dynamic braking on diesel locomotives. running-plate ;Steam locomotive :Foot-way that extends down the boiler sides and across the front of a locomotive. ;Diesel locomotive :Foot-way that encircles a locomotive on most types. S safety valve A valve that opens when pressure inside a boiler gets too great. sleeper Strip of wood or concrete that supports rails that are placed on top. Major part of a track. smokebox Place, usually at the front, in a steam locomotive where exhaust is mixed with steam and sent out the chimney. T tank locomotive A steam locomotive that does not use a tender, but instead uses integral bunker and water tank(s). tank engine tender A wagon that carries fuel and water for a steam locomotive, usually placed behind the footplate. track A pair of rails used to support and guide a locomotive. traction motor An electric motor on diesel-electric locomotives, electric locomotives and electric multiple units, that drives the axles to create motion. Traction motors are supplied with electricity to make them spin. truck A swiveling frame that carries axles on many steam, diesel and electric locomotives; the truck helps to guide the locomotive around corners. Elsewhere than North America these may be referred to as bogies. U unit Either one locomotive, or one car in a multiple unit. V valve Hole that opens and closes allowing the passage of fuel or steam. valve-gear Levers and rods that link the valves to the piston's movement on a steam locomotive. W weatherboard An upright, metal panel placed forward of the footplate on early, or cabless, steam locomotives in an attempt protect the driver and fireman. wheel arrangement The order of carrying and driving wheels on a locomotive; usually in a notation. Whyte notation Alt: Whyte's notation. A numerical method of classifying steam locomotives based on wheel arrangement. Numbers are separated by dashes. The first number defines the carrying wheels, the central number(s) defines the driving wheels and the last number defines the trailing wheels. X Y Z Category:Browse Category:Glossary